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Backyard rink calculator: board height on a sloped yard

Water always finds its level, so on a sloped yard the low end of the rink gets deep. Enter the rink size and how far the ground drops at each corner (the slope measuring guide shows how), and you get the board height for each side, the liner size, how much water it takes and how long the hose needs.

Units

Drop from a level string down to the ground at each corner (in). The highest corner has the smallest number.

The flow default (5 US gal/min, about 19 L/min) is a starting guess. To measure yours, time how long the hose takes to fill a 5 gallon bucket and divide 5 by the minutes.

Water needed
2,494 US gal
9,439 liters
Fill time
8 h 19 min
at the hose flow above
Deepest water
7 in
ground drop 4 in, average depth 5 in
Tallest board
9 in
liner 44 × 24 ft

At each corner

Front left
Water 3 in
Board 5 in
Front right
Water 4 in
Board 6 in
Back left
Water 6 in
Board 8 in
Back right
Water 7 in
Board 9 in

Board height per side

SideAt leastSmallest lumber that covers it
Front 6 in 2x8
Back 9 in 2x10
Left 8 in 2x10
Right 9 in 2x10

The height grows evenly from one corner to the next, so a side can step down toward its high corner. Rink kit boards come in their own heights; compare them with the "at least" column.

How to measure the corners

Drive a stake at each corner of the rink. The step-by-step guide has the details. Tie a string between two stakes, level it with a line level, and measure from the string down to the ground at each stake. Keep the same string height all the way around, so all four numbers start from the same level line.

The corner with the smallest number is the high point. The calculator puts the water there at the depth you chose, and every other point gets deeper by however much lower its ground is. The ground between corners is treated as a straight slope, so bumps and dips in the middle are not counted.

Assumptions behind the numbers

  • The water surface is level. The water volume is the rink area times the average depth over the four corners, which is exact for ground that slopes evenly between them.
  • Lumber heights are the actual sizes: 2x6 is 5.5 in, 2x8 is 7.25 in, 2x10 is 9.25 in and 2x12 is 11.25 in. The warning shows when a side needs more than a 2x12. It marks the tallest single board the calculator assumes, and says nothing about strength.
  • Liner size is the rink plus, on each side, the tallest board height and the overhang (liner = rink + 2 × (tallest board + overhang)). The overhang is how far the liner extends past the top of the boards and is adjustable above. It is rounded up to the next whole foot (or 10 cm). Liners are sold in fixed sizes, so pick the next size up.
  • Fill time is the volume divided by the hose flow. Water pressure varies a lot between houses, so a bucket test gives a better number than the default.
  • Ice takes up about 9% more room than the water it froze from. The numbers here are for liquid water.

Guides

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